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My New Single Seven

I've got my new Ruger Single Seven in hand now and I think I have a problem. I've slugged the barrel and checked the cylinder throats. Results are:

Barrel slug: .3134" (slightly tight where threaded into frame)

Throats: .315 using plug gauge

The problem arises because I intend to shoot only cast in this gun. If I use a boolit sized to .315, I don't think it will chamber. This possibility was suggested by 2 dogs. Since I don't have a tubing micrometer, I inserted a plug gauge into the .327 case and took a micrometer reading of the OD. From that I determined the wall thickness of the case to be .0127". If I seat a .315" boolit I end up with .3404" OD of the loaded round. A .340 plug gauge will not fit the chambers. A .313 boolit would give me a round that probably would chamber but would be .002 under throat size. Might even be a loose fit in the barrel.

All this is measurement and arithmetic so far. I don't have any boolits to actually load. Since standard practice is to fit the boolit to the throats, I don't know what to do at this point. I don't want to be forced to use jacketed bullets. I would appreciate any insight or suggestions.

BTW, I've messaged 2 dogs about this and may get a suggestion from him also.

I've had a 5 1/2" S7 since they were first issued by Lipseys. I cast and load .313 sized loobed with what ever is in the loobsizer. I used FC cases of many firings. It is amazing just how accurate the S7 is. I also have 2 of the 2016 production SP-101's in 327, the 4.2". I've never slugged or measured any of them; as they just worked to my satisfaction right from the start. I also have a 2" Taurus in 327; it shoots as well as any of the Rugers and the trigger is decidedly better than the Sp-101's. I first started out with 2 Charter Arms Target Bulldogs in 327, they were accurate but one died of a cracked frame and I sold the second. I wish you luck on your search for perfection with the new S7; it was an easy search for me.

Don't know if this helps ,but in March 2017 I bought a 4.2 inch SP101 327 mag.I used pin gauge on the cylinder throats and a .312 would slide in and a .313 would not. never bothered to slug the barrel. I size all my cast boolits at .313 and the gun shoots very well with no leading at all.I have at this time over 3000 rounds through the gun.
I would fire some factory loads and then see in a .315 size boolit would slide in a fired unsized case. If it does then I would size to .315

Thanks TC. The only problem is I don't have a .315 boolit. I held off ordering a mold from Accurate. It seemed kind of expensive to pay over $100 just to see if .315 would work. If it did work, then it would be worth it.

I'm tempted to see if I can return the gun and see if I can get one that has a cylinder more in line with what is available in molds and closer to the .312-.313 that you have. I suspect that Ruger would just tell me to shoot jacketed and that .315 is well within their tolerances.

I just checked several places on-line to order a box of factory ammo. Rarer than hen's teeth. Midway has some but everyone else that I have dealt with was "Out of Stock".

I have even thought of sending the cylinder to a custom smith and have the chamber reamed. The problem with that is that I don't know what size to ask for. This is getting to be a nightmare.

Contact Ruger. The H&R's I have seen [2] and the lone 327 ran closer to .3125 and 313. Verify your mike is accurate with a second one and that a factory jacketed bullet drops through without touching. Ask for a prepaid mailer to make it right.

I checked the throats with Meyer plug gauges. I then measured the gauge with my Brown & Sharp micrometer. Right on at .315.

Anyone willing to sell me a .313 jacketed bullet? All I have found with an internet search are .312 jacketed. I can buy .313 cast bullets too. I would also be interested in a .315 cast boolit. It was suggested that I seat a .315 bullet and see if it would chamber. I tried a back door method to see if this would chamber and it didn't even come close but I have no confidence in what I did.

I can purchase a box of .327 Federal from Midway. I would rather talk to Ruger first while the gun is unfired.

Is the S7 5 groove rifling? If so getting a good measurement is difficult. Start a thread asking for a few .315's and some jacketed to give it a try. Recently sent a gun back to Ruger for the second time and when asked which ammo I was using the first go round, I was told "we don't recommend reloads," but that didn't disqualify it from being serviced. BTW, it was a different model.

"Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same......." - Ronald Reagan

"It is foolish and wrong to mourn the men who died. Rather, we should thank God that such men lived." - George Patton

The second amendment is a nail on which hangs a picture of freedom - member Alex 4x4 Tver, Russia

I didn't count the grooves but I know it had an even number. I have measured several S&W barrel slugs using a V block that a member here supplied and got good numbers. If the Single Seven barrel had an odd number of grooves the measurement would have been way off.

You've encouraged me to talk to Ruger. I've been somewhat reluctant to get involved with them after hearing that some have been dismissed with statements such as "it is within tolerance". BTW, this gun is unfired. All I've got is my measurements.

Iv got a slew of 327s from the blackhawk to the gp100 and 101 sevens and Henry lever and shoot .313 cast in them all! If you ramp that.313 up, kick it in the rear hard, it will bump up, as long as you don't try to shoot too hard a bullet.

Everything I've read about .327's mentions that throats are usually .312-.313. I don't really want to start out at max loads. If I can get a .314 boolit to chamber in a loaded cartridge, I don't think that I would have to load real heavy. Right now I can't prove anything.

BTW. Ruger called back and said that .315+or-.001 is within tolerance. Surprise! Surprise!

I have two Ruger Single Sevens with something over 2500 rounds through them, plus an Sp101 with about 600 rounds through it. I suspect you are getting the cart before the horse. Until you shoot that revolver, measurements are merely numbers. They are suggestive, not guaranteed .313 has worked for all three of mine, with no leading, excellent groups, and high velocities. There was a fellow on this board who had a tag line that went something like "DR. Gun will give you the prescription for what will shoot." You might cool your jets until you get a couple hundred rounds down range. Buy a couple hundred .313 boolits from Rimrock or one of the other suppliers and give em a try.

_________________________________________________It's not that I can't spell: it is that I can't type.

If you order a .315 mold and can size to .314 I really think you'd be golden and have a shooter.

"Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same......." - Ronald Reagan

"It is foolish and wrong to mourn the men who died. Rather, we should thank God that such men lived." - George Patton

The second amendment is a nail on which hangs a picture of freedom - member Alex 4x4 Tver, Russia

John, if it was my gun, what I would try is a bullet right out of the mold. It would probably measure .3135" or better. I would want to shoot the greatest diameter bullet I could get to chamber so I would load me up a dummy and using my cylinder as a chamber gauge see how it fit.

If it fit, you would still run the risk of the propellant gasses blowing the lubricant out of the grease groove so I would avoid that problem by powder coating that bullet. Once the cast bullet is powder coated you can size it down until you get it to fit and not have to worry about gas blow by because there is no lubricant to lose and the powder coat does the work of the lubricant instead. I know you don't want to run a powder coated bullet, so go ahead and try the conventional ones first and see what you see. You never know because revolvers are all sorts of contrary contraptions and tend to avoid the rules.

The thing that you said that bothers me a bit is the restriction at the forcing cone. We might have to firelap the gun a little. Shoot it some and get back to me. You know how to find me. There are any number of guys on Singleactions.com that would send you a handful of powder coated cast bullets to try. Especially if you mailed them a postage paid padded mailer.

IF worse comes to worse, and you need a new cylinder and barrel, you have the perfect vehicle for a .257 Jackrabbit conversion!

Let me say something to you guys who have 32 caliber sixguns and have not had the throats properly corrected because they shoot "fine". The fact is, you might not be as Elmer Keith called it be "getting all you are holding for".

Take a look at this target. This is 4 of 5 bullets in 2 5/8s" inches at 100 yards with iron sights. I ain't posting this to say I am a great shot, I am posting it to point out to you the true potential of these little sixguns. I recommend and correct 32 caliber sixgun throats to .3133" and size all my bullets to .3135" for both my 32 H&R magnums and .327 Federals. This gives me a press fit in my 32's and the throats in my 327 are just shy of .314" so they work perfectly in that platform as well.

Guys, you cannot accurately measure your cylinder throats with a dial caliper. Nor can you get the exact diameter of your bullets. For a long time I have offered to measure your cylinder throats FREE OF CHARGE except for postage. I will also measure your cast bullets and check their hardness. If they need correction we will discuss that after. The fact that sixguns with less than proper dimensions shoot well is besides the point.

Back in the day when I could still see well enough, my SSM 5 1/2" would group 1 1/2" at 25yds from a rest. Factory .313 throats, .312 bore. guess I just lucked out. Sized the SAECO 325 to .314 and never looked back. Did that because that was the only 32 cal die I had (.303 Brit).

Finally checked bore and throats about 5yrs ago. Guess I just lucked out. What I really wanted was a 6 1/2' BISLEY. But when ever I found one I didn't have the money, and vice/versa.